Users who prefer a black background have to suffer slightly poorer graphic quality when seeing various icons that Revit uses. A good example of this is the Copy/Monitor tool. When you use this tool a little icon appears of a sine wave, EKG or "heartbeat" symbol.
I personally liked the old "evil eye", eyeball that used to show up...but I digress.
The point is that this icon is invisible when you use the black background. A VIDEO is equal to all these words.